Over a billion men, women and children worldwide smoke, and tobacco continues to be the largest single cause of premature death in developed countries. Nicotine, the main addictive component of tobacco, produces the neurophysiological, motivational and behavioural changes associated with nicotine addiction. Understanding the neuropharmacological, anatomical and behavioural underpinnings of the psychoactive effects of nicotine is key for the identification of new therapeutical targets and the development of new drugs against nicotine dependence. This proposal stems from recent data in the lab that pinpoint a novel mechanism of action for nicotine. We now show that the drug can change maturation and turnover of scaffolding proteins and neurotransmitter receptors by blocking proteasomal activity. Our data indicate that nicotine's effects on the proteasome occur via both nAChR-mediated and nAChR- independent mechanisms. These results provide a mechanism that could explain some of the effects of nicotine, including the drug-induced changes in protein levels, and nAChR upregulation. This exploratory grant will continue the characterization of the proteasome/nicotine interaction with both in vivo and in vitro mechanisms. To determine whether nicotine's influence on the proteasome is one of the mechanisms underlying the pharmacological effects of nicotine we will examine the behavioral effects of nicotine in mice in which proteasomal function is perturbed by proteasomal inhibitors or the inducible knockout of a proteasomal component. Other biochemical and pharmacological experiments will provide information on the nature of the nicotine/proteasome interaction. The investigation of nicotine's influence on the proteasome is important not only for the effects of nicotine on the brain but it will also provide new insights on the effects of tobacco on tissues and organs that do not express nAChRs.